This disclosure relates to exhaust emission control devices. More particularly, this disclosure relates to methods and apparatus for forming exhaust emission control devices.
The removal of emissions, such as hydrocarbon, carbon monoxide, nitrogen oxide, particulate matter, and the like, from the exhaust gases of internal combustion engines is required for cleaner operating vehicles. One focus area for such exhaust emission reduction has been in the area of post combustion treatment. Namely, post combustion treatment includes the placement of one or more exhaust emission control devices in the exhaust down stream of the internal combustion engine. Such exhaust emission control devices include catalytic converters, catalytic absorbers, diesel particulate traps, non-thermal plasma conversion devices, and the like.
Many exhaust emission control devices comprise a frangible or fragile structure that is prone to crushing and damage in the exhaust environment. For example, exhaust emission control devices have used a substrate, commonly made of ceramic (e.g., cordierite, carbon, and the like), with a high surface area for exposing the substrate to the exhaust gas. In the example where exhaust emission control device is a catalytic converter, the substrate has a catalytically active material supported thereon.
The substrate is often retained in the exhaust pipe housing by means of a retention material or mat. The retention material is adapted to retain the substrate in a housing and to seal the gap between the substrate and the housing to force the exhaust gas through the cellular structure of the substrate.
Disclosed herein is an apparatus and method for manufacturing an exhaust emission control device, and the exhaust emission control device formed thereby. The method of manufacturing an exhaust emission control device comprises: disposing a viscous-elastic material around at least a portion of a substrate to form a wrapped element. The wrapped element is compressed at a first compression rate and at a second compression rate that is slower than the first compression rate, and the wrapped element is introduced into a housing. Also disclosed is the exhaust emission control device formed by this method.
The apparatus for forming an exhaust emission control device comprises: a stuffing device having a conical portion comprising a first end, a transition point, and a second end. The first end has a first inner dimension. The transition point has a second inner dimension smaller than the first inner dimension, while the second end has a third inner dimension smaller than the second inner dimension and approximately equal to or smaller than the inner dimension of the housing. In addition, a first angle from the first end to the transition point is greater than a second angle from the transition point to the second end, and the second angle is greater than 0xc2x0.
The above-described and other features are appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.